The ordinary heat exchanger of the class here concerned with comprises a plurality of elongate parallel, laterally spaced fluid conducting tubes extending through a fluid conducting chamber or the like.
The tubes are established of material having high indices of heat conduction and have inlet and outlet ends communicating with means provided to conduct a first fluid medium to and from the tubes. The chamber through which the tubes extend has upstream and downstream ends communicating with means provided to conduct a second fluid medium through the chamber and about the exterior of the tubes.
In the ordinary heat exchanger, the tubes are straight, cylindrical in cross-section and are spaced one from the other a sufficient distance to afford most effective and efficient flow of the second fluid medium about and between them.
The cylindrical cross-section and required spacing of the tubes of ordinary heat exchangers determines and limits their density or surface compactness and their resulting efficiency, size and weight.
The cylindrical cross-section and required spacing of the tubes or ordinary heat exchangers work material limitations on the effectiveness and efficiency of the heat exchange attainable thereby and present inherent problems with respect to the headering or mounting of the ends of the tubes.
In accordance with and in furtherance of the foregoing, in heat exchangers of the character referred to above wherein the second medium is caused to flow about the tubes in a direction normal to the axes thereof, the spaces between the tubes have flow limiting or restricting effect which requires that the tubes be spaced a substantial distance apart and requires that the resulting heat exchanger structures be quite large, dimensionally. Further, such spacing of the cylindrical tubes results in a labyrinth-like series of passages of irregular shape defined by the cylindrical surfaces of adjacent related tubes. The irregular shape of the passages cause eddy currents and turbulence in the fluid medium flowing therethrough, which eddy currents and turbulence not only prevent uniform and efficient heat exchange, but also cause friction losses, attending pressure drop and the generation of heat, which adversely affect the efficiency and effectiveness of the heat exchangers.
The required spaced relationship of the tubes in ordinary heat exchangers requires the provision and use of costly complicated headering means for mounting the ends of the tubes which headering means most commonly include heavy complicated and costly to make header plates with multiplicities of through openings therein to receive and establish sealed engagement with the ends of the tubes related thereto. In such structures, each end of each tube must be separately engaged in a related opening in its related header plate and effectively fixed and sealed therein. Such a procedure of manufacture and/or assembly is time consuming, requires the exercise of special skills and is extremly costly. Further, the resulting structures are most often rather weak, subject to adverse thermal stresses and failure prone.
The art of heat exchangers of the general class here concerned with is extremely old and crowded. Throughout the years, to the present time, a great amount of time and engineering skill has been expended in the design and construction of heat exchanger structures. Throughout the years, there has long been a recognized want and need for exchangers having greater density or surface compactness than can be effectively attained with cylindrical tubes, but to date, the prior art has failed to provide a heat exchanger structure capable of attaining that end.